Craftsman who fabricate articles must from time to time grind beveled surfaces into workpieces. For example, crafters of knives may manually hold the tang of a knife against the moving surface of a grinding tool, such as a grinding belt. The tang of the knife may require being held at a particular angle, or at a reproducible angle so that the exact same bevel may be ground onto both sides of the final blade.
Experienced craftsmen who grind articles by hand can do a reasonably good job of setting the angle as desired. However, it takes many years to become sufficiently proficient as to be able to produce desired angles of bevels in this manner. Also, even an experienced craftsman may possibly lose control of the angle from time to time.
A particular situation when machine-like precision is desired is depicted in FIG. 6A. Grinding bevel surfaces 2, 4 into a blade blank 6 requires that both bevel surfaces 2, 4 be ground at the same angle A so as to result in a knife blade displaying bilateral symmetry. In FIG. 6A, the angle A is depicted as being that included angle spanning one of the bevel surfaces 2 or 4, and a plane 8 which bisects the blade bank 6 through the smallest dimension thereof. FIG. 6A illustrates the blade blank of a knife which may be produced by prior art methods.
FIG. 7 shows a prior art method of how the blade bank 6 may be ground by hand. The tang is held in the hand H of the operator against the belt 18 of a belt sanding or belt grinding machine 16. It will be appreciated that considerable skill, acuity, and experience are required of a human operator to keep the grinding angle constant, and further to keep the grinding angle equal to a predetermined desired angle. It is very difficult for a beginner to produce acceptable knives by hand grinding, and even for more experienced craftsmen to maintain a desired level of consistency in controlling angles of ground surfaces.
There exists a need in the prior art for an uncomplicated aid to assist in determining the exact angle of a workpiece which is to be held manually against the moving surface of a grinding tool.